ts: Export AccountsCoder (#439)

ts/src/index.ts

@@ -10,6 +10,7 @@ import Coder, {
   EventCoder,
   StateCoder,
   TypesCoder,
+  AccountsCoder,
 } from "./coder";
 import { Instruction } from "./coder/instruction";
 import { Idl } from "./idl";
@@ -56,6 +57,7 @@ export {
   EventCoder,
   StateCoder,
   TypesCoder,
+  AccountsCoder,
   Event,
   Instruction,
   setProvider,